Deflection amount estimating device, robot control device and method of estimating amount of deflection

Abstract

A deflection amount estimating device is provided for estimating an amount of deflection of a four-bar linkage structure part of a robotic arm. The four-bar linkage structure part swings in a given angle range. The deflection amount estimating device comprises processing circuitry configured to calculate a swing angle of the four-bar linkage structure part; calculate a load received by the four-bar linkage structure part, determine a stiffness value, corresponding to the swing angle of the four-bar linkage structure part, based on a stiffness-value determining function indicating a correlation between the stiffness value and the swing angle of the four-bar linkage structure part, the stiffness value indicating a value of each element in a stiffness matrix associating the load with the amount of deflection of the four-bar linkage structure part; and calculate the amount of deflection of the four-bar linkage structure part based on the load and the stiffness matrix.

What is claimed is: 
     
       1. A deflection amount estimating device for estimating an amount of deflection of a four-bar linkage structure part of a robotic arm comprised of a plurality of links coupled to each other via joints, the robotic arm including the four-bar linkage structure part configured to swing in a given angle range, the deflection amount estimating device comprising:
 processing circuitry configured to
 calculate a swing angle of the four-bar linkage structure part; 
 calculate a load received by the four-bar linkage structure part; 
 determine a stiffness value, corresponding to the swing angle of the four-bar linkage structure part, based on a stiffness-value determining function indicating a correlation between the stiffness value and the swing angle of the four-bar linkage structure part, the stiffness value indicating a value of each element in a stiffness matrix associating the load received by the four-bar linkage structure part with the amount of deflection of the four-bar linkage structure part; and 
 calculate the amount of deflection of the four-bar linkage structure part based on the load received by the four-bar linkage structure part and the stiffness matrix having the stiffness value elements. 
 
 
     
     
       2. The deflection amount estimating device of  claim 1 , wherein the four-bar linkage structure part has a closed linkage structure. 
     
     
       3. The deflection amount estimating device of  claim 1 , wherein the four-bar linkage structure part has a parallel-linkage structure. 
     
     
       4. The deflection amount estimating device of  claim 1 , wherein the processing circuitry obtains the stiffness-value determining function by
 acquiring the stiffness value corresponding to each of a plurality of different swing angles by an analysis in advance, and 
 linearly interpolating the stiffness values acquired by the analysis corresponding to the plurality of swing angles. 
 
     
     
       5. A robot control device, comprising:
 the robotic arm including the four-bar linkage structure part; and 
 the deflection amount estimating device of  claim 1 . 
 
     
     
       6. The robot control device of  claim 5 , wherein
 the robot control device includes control circuitry that generates a command value, for controlling the robotic arm, by calculating an amount of compensation corresponding to the amount of deflection. 
 
     
     
       7. The robot control device of  claim 6 , wherein the control device is further configured to control the robotic arm according to the command value. 
     
     
       8. The robot control device of  claim 6 , wherein the command value reduces a vibration of the robotic arm caused by acceleration of the robotic arm. 
     
     
       9. A method of estimating an amount of deflection of a four-bar linkage structure part of a robotic arm comprised of a plurality of links coupled to each other via joints, the robotic arm including the four-bar linkage structure part configured to swing in a given angle range, the method comprising:
 calculating a swing angle of the four-bar linkage structure part; 
 calculating a load received by the four-bar linkage structure part; 
 determining a stiffness value, corresponding to the calculated swing angle of the four-bar linkage structure part, based on a stiffness-value determining function indicating a correlation between the stiffness value and the swing angle of the four-bar linkage structure part, the stiffness value indicating a value of each element in a stiffness matrix associating the load received by the four-bar linkage structure part with the amount of deflection of the four-bar linkage structure part; and 
 calculating the amount of deflection of the four-bar linkage structure part based on the calculated load received by the four-bar linkage structure part and the stiffness matrix having the determined stiffness value elements. 
 
     
     
       10. The method of  claim 9 , wherein the four-bar linkage structure part has a closed linkage structure. 
     
     
       11. The method of  claim 9 , wherein the four-bar linkage structure part has a parallel-linkage structure. 
     
     
       12. The method of  claim 9 , further comprising obtaining the stiffness-value determining function by
 acquiring the stiffness value corresponding to each of a plurality of different swing angles by an analysis in advance, and 
 linearly interpolating the stiffness values acquired by the analysis corresponding to the plurality of swing angles. 
 
     
     
       13. A system, comprising:
 a robotic arm comprised of a plurality of links coupled to each other via joints and a four-bar linkage structure part, the four-bar linkage structure part configured to swing in a given angle range; and 
 processing circuitry configured to
 calculate a swing angle of the four-bar linkage structure part; 
 calculate a load received by the four-bar linkage structure part; 
 determine a stiffness value, corresponding to the swing angle of the four-bar linkage structure part, based on a stiffness-value determining function indicating a correlation between the stiffness value and the swing angle of the four-bar linkage structure part, the stiffness value indicating a value of each element in a stiffness matrix associating the load received by the four-bar linkage structure part with an amount of deflection of the four-bar linkage structure part; and 
 calculate the amount of deflection of the four-bar linkage structure part based on the load received by the four-bar linkage structure part and the stiffness matrix having the stiffness value elements. 
 
 
     
     
       14. The system of  claim 13 , wherein the four-bar linkage structure part has a closed linkage structure. 
     
     
       15. The system of  claim 13 , wherein the four-bar linkage structure part has a parallel-linkage structure. 
     
     
       16. The system of  claim 13 , wherein the processing circuitry obtains the stiffness-value determining function by
 acquiring the stiffness value corresponding to each of a plurality of different swing angles by an analysis in advance, and 
 linearly interpolating the stiffness values acquired by the analysis corresponding to the plurality of swing angles. 
 
     
     
       17. The system of  claim 13 , wherein the processing circuitry is further configured to generate a command value, for controlling the robotic arm, by calculating an amount of compensation corresponding to the amount of deflection. 
     
     
       18. The system of  claim 17 , wherein the processing circuitry is further configured to control the robotic arm according to the command value. 
     
     
       19. The system of  claim 17 , wherein the command value reduces a vibration of the robotic arm caused by acceleration of the robotic arm.